Gas discharge lamps, such as neon lamps, have in the past been energized by a line frequency voltage source operating through a step-up transformer which has usually been termed a "ballast." In such prior art circuits, the transformer has been operating at line frequency, typically 50 or 60 hertz, and this necessarily means a physically large and bulky transformer with a considerable amount of iron to carry this low frequency flux.
Fluorescent lamps have been operated on high frequency, e.g., 24 kHz, as shown in U.S. Pat. No. 4,042,852. This permits the use of a much smaller physical size of transformer or ballast, because not as much iron is required for high frequency operation. This circuit required a relatively high-power starter circuit utilizing a thyristor. When this high frequency type of circuit is attempted to be used on a gas discharge lamp, such as a neon lamp, as distinguished from a fluorescent lamp, striations or bubbles in the gas plasma within the lamp are formed, which have been found to be objectionable from a visibility and marketing standpoint. These striations are produced in the high frequency circuits for fluorescent lamps, but since fluorescent lamps have an internal coating, such striations are masked. Also, in such prior art circuits, there was provided a full-wave, two-transistor oscillator to supply the primary of the transformer, and the drive was balanced, which we have found to produce striations if the circuit were to be used on a gas discharge lamp such as a neon lamp.